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From: Matthew Wilcox <willy@infradead.org>
To: Yang Shi <shy828301@gmail.com>
Cc: Hugh Dickins <hughd@google.com>, Zi Yan <ziy@nvidia.com>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Kent Overstreet <kent.overstreet@gmail.com>,
	Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux MM <linux-mm@kvack.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Darrick J. Wong" <djwong@kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	David Howells <dhowells@redhat.com>,
	Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: Mapcount of subpages
Date: Fri, 24 Sep 2021 02:31:34 +0100	[thread overview]
Message-ID: <YU0qdpbjK5Hdfk2p@casper.infradead.org> (raw)
In-Reply-To: <CAHbLzkp__irFweEZMEM-CMF_-XQpJcW1dNDFo=RnqaSTGtdJkg@mail.gmail.com>

On Thu, Sep 23, 2021 at 06:11:19PM -0700, Yang Shi wrote:
> On Thu, Sep 23, 2021 at 4:49 PM Hugh Dickins <hughd@google.com> wrote:
> > I believe Yang Shi is right insofar as the decision on whether it's worth
> > queuing for deferred split is being done based on those subpage _mapcounts.
> > That is a use I had not considered, and I've given no thought to how
> > important or not it is.
> 
> Anyway deferred split is anon THP specific. We don't have to worry
> about this for file THP. So your suggestion about just counting total
> mapcount seems feasible to me for file THP at least.

But I think we probably *should* do deferred split for file THP.
At the moment, when we truncate to the middle of a shmem THP, we try
a few times to split it and then just give up.  We should probably try
once and then queue it for deferred split.

  reply	other threads:[~2021-09-24  1:33 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-23  1:21 Struct page proposal Kent Overstreet
2021-09-23  3:23 ` Matthew Wilcox
2021-09-23  5:15   ` Kent Overstreet
2021-09-23 11:40     ` Mapcount of subpages Matthew Wilcox
2021-09-23 12:45       ` Kirill A. Shutemov
2021-09-23 21:10         ` Hugh Dickins
2021-09-23 21:54           ` Yang Shi
2021-09-23 22:23             ` Zi Yan
2021-09-23 23:48               ` Hugh Dickins
2021-09-24  0:25                 ` Zi Yan
2021-09-24  0:57                   ` Hugh Dickins
2021-09-24  1:11                 ` Yang Shi
2021-09-24  1:31                   ` Matthew Wilcox [this message]
2021-09-24  3:26                     ` Yang Shi
2021-09-24 23:05           ` Kirill A. Shutemov
2021-09-23 18:56       ` Mike Kravetz
2021-09-23  9:03 ` Struct page proposal David Hildenbrand
2021-09-23 15:22   ` Kent Overstreet
2021-09-23 15:34     ` David Hildenbrand
2021-09-27 17:48 ` Vlastimil Babka
2021-09-27 17:53   ` Kent Overstreet
2021-09-27 18:34     ` Linus Torvalds
2021-09-27 20:45       ` David Hildenbrand
2021-09-27 18:05   ` Matthew Wilcox
2021-09-27 18:09     ` Kent Overstreet
2021-09-27 18:12       ` Matthew Wilcox
2021-09-27 18:16         ` David Hildenbrand
2021-09-27 18:53           ` Vlastimil Babka
2021-09-27 19:04             ` Linus Torvalds
2021-09-27 18:16         ` Kent Overstreet
2021-09-28  3:19           ` Matthew Wilcox
2021-09-27 19:07       ` Vlastimil Babka
2021-09-27 20:14         ` Kent Overstreet
2021-09-28 11:21         ` David Laight
2021-09-27 18:33     ` Kirill A. Shutemov

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